检查客户端套接字是否在服务器上关闭

Question

如何在服务器端检查客户端是否关闭了套接字？

我有这个服务器，它等待连接然后 return 10 条消息到客户端：

public class SocketServidor {
    static ServerSocket serverSocket;

    public static void main(String[] args) throws Exception {
        serverSocket = new ServerSocket(5963);
        while(true) {
            final Socket socket = serverSocket.accept();
            new Thread(() -> {
                try {
                    PrintWriter out = new PrintWriter(socket.getOutputStream());
                    for (int i = 0; i < 10; i++) {
                        int valor = (int) (Math.random() * 5) + 1;
                        out.println("Você acabou de ganhar R$ "+new DecimalFormat("###,##0.00").format(valor)+"!");
                        out.flush();
                        Thread.sleep(valor*1000);
                    }
                    socket.close();
                } catch (Exception ex) {
                    Logger.getLogger(SocketServidor.class.getName()).log(Level.SEVERE, null, ex);
                }
            }).start();
        }
    }
}

客户端只读取值，但在第五次读取时停止：

public class SocketCliente {

    public static void main(String[] args) throws Exception {
        Socket socket = new Socket("localhost", 5963);
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        String leitura;
        int lidas = 0;
        while((leitura = in.readLine()) != null) {
            lidas++;
            System.out.println(leitura);
            if(lidas == 5){
                socket.close();
            }
        }
    }

}

问题是，即使在第五次读取之后，当客户端关闭套接字时，服务器仍继续向客户端发送消息。如何在客户端关闭套接字时关闭服务器端的套接字？

Answer 1

异常被 PrintWriter.flush()
抑制您看不到异常，因为 PrintWriter.flush() 抑制了异常。要检查 PrintWriter.println() 之后的错误状态，您可以使用 PrintWriter.checkError() 而不是 flush()。或者，您可以使用 OutputStreamWriter 而不是 PrintWriter，这样异常就不会被抑制。

有checkError

serverSocket = new ServerSocket(5963);
while(true) {
    final Socket socket = serverSocket.accept();
    new Thread(() -> {
        try {
            PrintWriter out = new PrintWriter(socket.getOutputStream());
            for (int i = 0; i < 10; i++) {
                int valor = (int) (Math.random() * 5) + 1;
                out.println("Você acabou de ganhar R$ "+new DecimalFormat("###,##0.00").format(valor)+"!");
                //out.flush();
                if(out.checkError()){
                    System.out.println("Error. Break");
                    break;
                }
                Thread.sleep(valor*1000);
            }
            socket.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }).start();
}

带OutputStreamWriter

serverSocket = new ServerSocket(5963);
while(true) {
    final Socket socket = serverSocket.accept();
    new Thread(() -> {
        try {
            Writer out = new OutputStreamWriter(socket.getOutputStream());
            for (int i = 0; i < 10; i++) {
                int valor = (int) (Math.random() * 5) + 1;
                out.write("Você acabou de ganhar R$ "+new DecimalFormat("###,##0.00").format(valor)+"!");
                out.write("\r\n");
                out.flush();
                Thread.sleep(valor*1000);
            }
            socket.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }).start();
}

检查客户端套接字是否在服务器上关闭

Check if client socket is closed on the server

java

sockets